Aircraft typically include a plurality of flight control surfaces that, when controllably positioned, guide the movement of the aircraft from one destination to another. The number and type of flight control surfaces included in an aircraft may vary, but typically include both primary flight control surfaces and secondary flight control surfaces. The primary flight control surfaces are those that are used to control aircraft movement in the pitch, yaw, and roll axes, and the secondary flight control surfaces are those that are used to influence the lift or drag (or both) of the aircraft.
In some aircraft, the positions of the aircraft flight control surfaces may be controlled via input from the flight crew and/or via an autopilot system. The autopilot system generates appropriate position commands that move at least some of the aircraft flight control surfaces (e.g., the primary flight control surfaces) to desired positions. In most instances, this movement is effected via actuators that are coupled to the flight control surfaces. In some autopilot systems, some or all of the actuators are electromechanical actuators. Electromechanical actuators typically include an electric motor that receives motor commands from a controller. In response to these motor commands, the motor generates torque, which is transmitted to an actuator that in turn effects movement of a flight control surface.
Preferably, the motor commands are such that the power dissipation by the motor is sufficiently low, or over sufficiently short time intervals, that the motor can comply with the commands without overheating. However, there may be instances in which this is not the case. Thus, it may be desirable to measure motor temperature and, based on the measured temperature, limit motor power to prevent such overheating. Yet, it is typically impractical to measure the temperature of the motor directly, since its rotation can make attachment of a temperature sensor difficult, if not unfeasible.
Hence, there is a need for a system and method of monitoring and controlling motor temperature to ensure that the motor will not overheat, and that does not rely on a direct measurement of motor temperature. The present invention addresses at least this need.